Prior to the present invention, it has been known to react acetone with formaldehyde to obtain methyl vinyl ketone. See Embers U.S. Pat. No. 3,928,457. This patent asserts that "yields of up to 82% methyl vinyl ketone, based on formaldehyde, can be expeditiously obtained." Efficiencies with respect to acetone, however, are not as good. The '457 patent requires a catalyst of phosphoric or sulfuric acid.
A general reaction for the preparation of an alpha, beta unsaturated ketone by catalytic vapor phase condensation of formaldehyde and a ketone is disclosed in U.S. Pat. No. 3,928,458. In Table VI, the use of acetone is shown; the catalyst is a silica gel.
Alpha, beta-unsaturated ketones have been prepared by reacting ketones with formaldehyde or methanol at elevated temperatures in the presence of a heterogeneous catalyst. See equation 1. Both vapor-phase and liquid-phase processes have been used to accomplish this. See U.S. Pat. Nos. 3,578,702 and 2,451,251; British Patent No. 993,389. ##STR1##
However, these processes are generally uneconomical because of short-lived catalyst activity which results from the tendency of MVK and/or formaldehyde to polymerize on the surface of the catalyst. Consequently, frequent replacement or regeneration of the solid catalysts is necessary.
There are other liquid-phase processes for producing MVK discussed in the literature. One process relates to initially generating 3-keto-1-butanol from acetone and aqueous formaldehyde. See U.S. Pat. No. 3,544,634. MVK is produced by dehydration in the presence of aluminum oxide.
This particular process is limited because MVK is not formed directly and a mixture of polymethylol compounds is formed along with the desired keto-alcohol which must be separated. Another disclosure concerns generation of MVK from acetone, aqueous formaldehyde, and a strong acid (H.sub.2 SO.sub.4, H.sub.3 PO.sub.4, HCl, HBr, HI or p-toluenesulfonic acid). See U.S. Pat. Nos. 3,928,457 and 2,848,499. This method requires relatively harsh reaction conditions of temperature, pressure and acid dissociation constant (10.sup.-4 or greater) while still only resulting in acetone conversions of less than 10%.
The literature also teaches the separate use of secondary amines and strong acid or weak acid salts of secondary amines for the reaction of ketones and, primarily, aldehydes, with aqueous formaldehyde (monomeric) to form the corresponding vinyl aldehyde and ketones (see Ai, M. J., Catal., 1987, 106, 2734; Ueda, W. Yokoyama, T., Moro-Oka, Y., Ikawa, T., J. Chem. Soc., Chem., Commun., 1984, 39.; Gutsche, D. C., Nam., K. C., J. Am. Chem. Soc., 1988, 110, 6153; U.S. Pat. Nos. 4,275,242, 4,343,239, 4,406,079 and 4,496,770).
The reader may also be interested in reviewing U.S. Pat. Nos. 4,374,274, 3,928,450 and 3,701,798. The '798 patent uses an oxide of a rare earth metal as a catalyst.